The editing data put ArtboardArray and AIDocumentCanvasSize in the part
of the /Document dictionary marked /NotRecorded. Apps that read the editing
data do not read artboards from there: a file opened with one default
artboard the size of the first, the other artboards and the names were
lost, and the art landed one artboard's height above it. The two entries
now close a /Recorded part, followed by an empty /NotRecorded one, as in
the files users sent.